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Test Info:
- This WPT test may be referenced by the following Test IDs:
- /custom-elements/htmlconstructor/newtarget.html - WPT Dashboard Interop Dashboard
<!DOCTYPE html>
<title>Custom Elements: [HTMLConstructor] derives prototype from NewTarget</title>
<meta name="author" title="Domenic Denicola" href="mailto:d@domenic.me">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../resources/custom-elements-helpers.js"></script>
<body>
<script>
"use strict";
test_with_window(w => {
let beforeDefinition = true;
const proto1 = { "proto": "number one" };
const proto2 = { "proto": "number two" };
function TestElement() {
const o = Reflect.construct(w.HTMLElement, [], new.target);
assert_equals(Object.getPrototypeOf(o), proto2,
"Must use the value returned from new.target.prototype");
assert_not_equals(Object.getPrototypeOf(o), proto1,
"Must not use the prototype stored at definition time");
}
const ElementWithDynamicPrototype = new Proxy(TestElement, {
get: function (target, name) {
if (name == "prototype")
return beforeDefinition ? proto1 : proto2;
return target[name];
}
});
w.customElements.define("test-element", ElementWithDynamicPrototype);
beforeDefinition = false;
new ElementWithDynamicPrototype();
}, "Use NewTarget's prototype, not the one stored at definition time");
test_with_window(w => {
// We have to not throw during define(), but throw during super()
let throws = false;
let err = { name: "prototype throws" };
function TestElement() {
throws = true;
assert_throws_exactly(err, () => {
Reflect.construct(w.HTMLElement, [], new.target);
});
}
const ElementWithDynamicPrototype = new Proxy(TestElement, {
get: function (target, name) {
if (throws && name == "prototype")
throw err;
return target[name];
}
});
w.customElements.define("test-element", ElementWithDynamicPrototype);
new ElementWithDynamicPrototype();
}, "Rethrow any exceptions thrown while getting the prototype");
[null, undefined, 5, "string"].forEach(function (notAnObject) {
test_with_window(w => {
// We have to return an object during define(), but not during super()
let returnNotAnObject = false;
function TestElement() {
const o = Reflect.construct(w.HTMLElement, [], new.target);
assert_equals(Object.getPrototypeOf(new.target), window.Function.prototype);
assert_equals(Object.getPrototypeOf(o), window.HTMLElement.prototype,
"Must use the HTMLElement from the realm of NewTarget");
assert_not_equals(Object.getPrototypeOf(o), w.HTMLElement.prototype,
"Must not use the HTMLElement from the realm of the active function object (w.HTMLElement)");
return o;
}
const ElementWithDynamicPrototype = new Proxy(TestElement, {
get: function (target, name) {
if (name == "prototype")
return returnNotAnObject ? notAnObject : {};
return target[name];
}
});
w.customElements.define("test-element", ElementWithDynamicPrototype);
returnNotAnObject = true;
new ElementWithDynamicPrototype();
}, "If prototype is not object (" + notAnObject + "), derives the fallback from NewTarget's realm (autonomous custom elements)");
test_with_window(w => {
// We have to return an object during define(), but not during super()
let returnNotAnObject = false;
function TestElement() {
const o = Reflect.construct(w.HTMLElement, [], new.target);
assert_equals(Object.getPrototypeOf(new.target), window.Function.prototype);
assert_equals(Object.getPrototypeOf(o), window.HTMLElement.prototype,
"Must use the HTMLElement from the realm of NewTarget");
assert_not_equals(Object.getPrototypeOf(o), w.HTMLElement.prototype,
"Must not use the HTMLElement from the realm of the active function object (w.HTMLElement)");
return o;
}
// Create the proxy in the subframe, which should not affect what our
// prototype ends up as.
const ElementWithDynamicPrototype = new w.Proxy(TestElement, {
get: function (target, name) {
if (name == "prototype")
return returnNotAnObject ? notAnObject : {};
return target[name];
}
});
w.customElements.define("test-element", ElementWithDynamicPrototype);
returnNotAnObject = true;
new ElementWithDynamicPrototype();
}, "If prototype is not object (" + notAnObject + "), derives the fallback from NewTarget's GetFunctionRealm (autonomous custom elements)");
});
</script>
</body>